Add fmt::Debug constraint to BitFlagNum

Otherwise, `T: Debug` isn't enough to imply `BitFlags<T>: Debug`, and
this can get in the way of code generated by #[derive(Debug)].

Author: arcnmx

enumflags/src/formatting.rs

@@ -4,7 +4,6 @@ use crate::{BitFlags, _internal::RawBitFlags};
 impl<T> fmt::Debug for BitFlags<T>
 where
     T: RawBitFlags + fmt::Debug,
-    T::Type: fmt::Binary + fmt::Debug,
 {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         let name = T::bitflags_type_name();

enumflags/src/lib.rs

@@ -89,6 +89,7 @@ pub mod _internal {
 
     use core::ops::{BitAnd, BitOr, BitXor, Not};
     use core::cmp::PartialOrd;
+    use core::fmt;
 
     pub trait BitFlagNum
         : Default
@@ -97,6 +98,8 @@ pub mod _internal {
         + BitXor<Self, Output = Self>
         + Not<Output = Self>
         + PartialOrd<Self>
+        + fmt::Debug
+        + fmt::Binary
         + Copy
         + Clone {
     }

test_suite/tests/formatting.rs

@@ -72,3 +72,13 @@ fn format() {
         "0x0F"
     );
 }
+
+#[test]
+fn debug_generic() {
+    use enumflags2::{BitFlags, _internal::RawBitFlags};
+
+    #[derive(Debug)]
+    struct Debug<T: RawBitFlags>(BitFlags<T>);
+
+    let _ = format!("{:?}", Debug(BitFlags::<Test>::all()));
+}